Nickel cobalt chromium alloy



July 19, 1955 G. T. HARRIS ETAL 2,713,538

NICKEL COBALT CHROMIUM ALLOY Filed Jan. 24, 1951 5 Sheets-Sheet l IO I2I4 CARBIDE-FORMING ELEMENTS: PER CENT l EFFECT OF COMPOSITION 0N RUPTURETIME OF COBALT BASE ALLOYS WITH VrM02Nb= I:|:I- TEST CONDITIONS STRESSI4 TONS/SQ. IN. AT 750 C.

F l G.

9 'n d 'f c. T o O o o o N39 aad Noauvo INVENTORS- GEOFFREY THOMASHARRIS GHENRY CAVE CHILD MWL/#Mimi ATTORNEYS.

July 19, 1955 G. Tr HARRIS ET AL 2,713,538

NICKEL COBALT CHROMIUM ALLOY Filed Jan. 24, i951 3 Sheets-Sheet 2 EFFECTOF COMPOSITION ON CREEP PROPERTIES FOR COBALT- -BASE-ALLOYS WITHV=Mo=Nb=ll=l AND O25/o CARBON CONTENT.

TIME HOURS 2 4 6 8 IO I2 CARBIDE FORMING ELEMENTS (V+ Mo+ Nb)=PER.CENT.

INVENToRs.

GEoFFREY THoMAs HARRIS F IG. 2. a HENRY cAvE cHlLD bM/L/a/AJ/d/Lu/ZATTORNEYS.

July 19, 1955 G. T. HARRIS ET AL 2,713,538

I NICKEL COBALT CHROMIUM ALLOY Filed Jan. 24, 1951 3 Sheets-Sheet 5EFFECT oF coMPoslTloN oN THE RUPTURE TIME Fon coBALT BAsE ALLoYs wlTHv+M+Nb=6% AND @25% cARBoN TEsT coNo|cT|oNs= |4ToNs/so-m. AT 750 c.

Mo# PER CENT 347 TIME (HOURS) T0 RUPTURE |00 u u u IN V EN TORS.

GEOFFREY THOMAS HARRIS a HENRY CAVE CHILD ATTORNEYS.

United States Patent() NICKEL COBALT `CHROMIUM ALLOY Geoffrey ThomasHarris and Henry Cave Child, Shellield, England, assignors to WilliamJessop & Sons Limited, Sheiield, England, a British company ApplicationJanuary 24, 1951, Serial No. 207,551 2 Claims. (Cl. 7.5--171) Thisinvention is concerned with alloys which have a high degree ofresistance to creep at elevated temperatures, and this application is acontinuation-impart of our co-pending application Serial No. 9,325, ledthe 18th of February 1948, now abandoned.

Alloys having as essential constituents carbon, co-

balt, nickel, chromium, carbide-forming elements such as niobium,molybdenum and vanadium, deoxidizing agents such as manganese andsilicon, and the remainder iron, are known to possess desirableproperties such as, for example, their resistance to creep, whenoperated under stress at high temperatures.

As a result of experimental research upon alloys having these essentialconstituents, we have found that such properties are markedly superiorwhen the ratio of carbide-forming elements to carbon in the alloys iscarefully balanced and when the optimum ratio of one carbide-formingelement to another is used.

Initially our experiments were directed to alloys having cobalt, nickeland iron in the ratio 40:15 :15, with 19% by weight of chromium and theusual small amounts of the deoxidizers manganese and silicon, e. g. 0.8%and 0.3% respectively. The carbon content and the carbide-formingcontent were varied (the carbide-forming elements vanadium, molybdenumand niobium being used and being in the ratio lzlzl), the carbon contentextending upwardly from 0.05% and the carbid'e forming content extendingupwardly from 2.7%. Each such alloy was normalized from 1280z C. and thetime taken to rupture for each alloy under a stress of 14 tons persquare inch at 750 C. was determined.

The results obtained are shown graphically in Figure l oftheaccompanying drawings. It will be seen from this figure that for suchalloys the time to rupture under a stress of 14 tons per square inch isdependent on the ratio of carbon to carbide forming elements. For eachcarbon content there is an optimum content of the carbide formingelements, e. g. at 0.25% carbon there should be a total of 6% of thecarbide forming elements. This optimum content of the carbide formingelements varies directly as the carbon content and there is asubstantial increase in the fracture time of the optimum alloy as thecarbon content is raised.

The next experiments were carried out on similar alloys under similarconditions, but the carbon content was maintained fixed at 0.25%, andthe carbide-forming content was varied between about 3.2% and 12%. lneach case the carbide-forming elements vanadium, molybdenum and niobiumagain were in the ratio l:1:l.

Figure 2 shows the eilect of Varying the carbide-forming content of thealloys upon the creep properties of the alloys, the curves showing thetime for 1% creep strain, the time for 1.5% creep strain and the time tofracture. It will be seen from these curves that better creep propertiesare obtained when the carbide-forming elements are present in an amountbetween about 5.4% and about 7.5%. l

Further tests under similar conditions were carried 2,713,538 PatentedJuly 19, 1955 ICC out on alloys having 0.25% of carbon and 6% ofcarbideforming elements, the ratio of one carbide-forming element toanother being varied. Figure 3 shows the elect of the varying of theproportions of the individual carbide-forming elements on the rupturetime of the alloys, and from the curves obtained it will be seen that,for optimum results:

(a) Vanadium rnust be present in an amount between substantially 1% andsubstantially 5%;

(b) Molybdenum must be present in an amount between substantially 0.5%and substantially 3%; and

(c) Niobium may be absent but, if present, must not exceed 3%.

Subsequent investigations showed that these relationships generallyremain true under different test condi tions of temperature and stress.

Bearing in mind these relationships between the carbide-forming elementsthemselves and between the percentage of carbon and carbide-formingelements, a larger number of alloys having the same constituents butwith the individual contents varied over a narrow range wereinvestigated and we have found that optimum properties are obtained withan alloy which has the following constituents:

Per cent Carbon 0.3 Silicon 0.3 Manganese 0.8 Nickel l2 Chromium 19Molybdenum 2 Niobium 1.2 Vanadium 2.8 Cobalt 45 Iron (with unavoidableimpurities) 16.6

An alloy of this composition was solution treated at l280 C. for l5minutes followed by quenching in oil.l 'After this treatment bars wereaged at a temperature of 750 C. for 46 hours and a typical test gave thefollowing results. Under a stress of 14 tons per square inch at atemperature of 750 C., 1% creep extension was reached in 1340 hours andrupture occurred in 1636 hours, the minimum creep rate being 4.7)(10-6per hour and the iinal elongation being 4%.

Generally these properties were substantially retained not only byalloys falling within the shaded areas of Figures l and 3, but also byalloys having their essential constituents within the narrow range:

Per cent Carbon 0.25-0.35

Silicon 0.2-0.6

Manganese 0.6-1 Nickel 10-15 Chromium 18-20 Molybdenum 1.8-2.3

Niobium ll.4

Vanadium 2.63.l Cobalt 42-46 Iron (with unavoidable impurities)Remainder It will be appreciated that molybdenum may be replaced wholly,or in part, by tungsten and that niobium is intended not only to meanniobium alone but also to mean niobium in combination with tantalum, thetantalum either being added intentionally or occurring as an impurity,since niobium is rarely, if ever, obtained on a commercial scale freefrom tantalum. Where niobium is combined with tantalum it is desirablefor the proportion of niobium to be at least 0.5

What is claimed is:

l. An alloy consisting of the following elements in about theproportions specified:

Per cent Carbon 0.3 Silicon 0.3 Manganese 0.8 Nickel l2 Chromium 19Molybdenum 2 Niobiurn with tantalum 1.2 Vanadium 2.8

Cobalt 45 Iron (with unavoidable impurities) 16.6

2. Alloys consisting of the following elements: carbon not exceedingabout 0.35%; small amounts of silicon and manganese within about theranges silicon 0.2 to 0.6% and manganese 0.6 to 1.0%; nickel 10 to 15%;chromium 18 to 20%; and the following three carbideforming elements,namely, molybdenum, niobium and vanadium; cobalt 42 to 46%; and theremainder iron with unavoidable impurities: the combined percentages ofthe said carbide-forming elements being between i about 5.4% and 7.5%;the individual percentages of the References Cited in the file of thispatent UNITED STATES PATENTS 2,246,078 Rohn et al. June 17, 19412,513,470 Franks et al. July 4, 1950 2,537,477 Mohling et al. Jan. 9,1951 FOREIGN PATENTS 510,154 Great Britain July 24, 1939

2. ALLOYS CONSISTING OF THE FOLLOWING ELEMENT: CARBON NOT EXCEEDINGABOUT 0.35%; SMALL AMOUNTS OF SILICON AND MANGANESE WITHIN ABOUT THERANGES SILICON 0.2 TO 0.6% AND MANGANESE 0.6 TO 1.0%; NICKLE 10 TO 15%CHROMIUM 18 TO 20%; AND THE FOLLOWING THREE CARBIDEFORMING ELEMENTS,NAMELY, MOLYBDENUM, NIOBIUM AND VANADIUM; COBALT 42 TO 46%; AND THEREMAINDER IRON WITH UNAVOIDABLE IMPURITIES: THE COMBINED PERCENTAGES, OFTHE SAID CARBIDE-FORMING ELEMENTS BEING BETWEEN ABOUT 5.4% AND 4.5%; THEINDIVIDUAL PERCENTAGES OF THE SAID CARBIDE-FORMING ELEMENTS BEINGMOLYBDENUM BETWEEN ABOUT 1.8 AND 2.3%; VANADIUM BETWEEN ABOUT 2.6 AND3.1%; AND NIOBIUM BETWEEN ABOUT 1.0 AND 1.4%; THE CARBON CONTENT AND THECORRESPONDING TOTAL CONTENT OF THE CARBIDE-FORMING CONSTITUENTS FALLINGWITHIN THE SHADED AREA OF FIGURE 1 OF THE ACCOMPANYING DRAWINGS.